14. Use of male-sterile genetic stocks for precise estimation of linkage intensities in backcrossed progenies

Toshiro Kinoshita, Plant Breeding Institute, Faculty of Agriculture, Hokkaido University, Sapporo, 060 Japan.


Cytoplasmic male-sterile (CMS) lines with marker genes were raised by recurrent backcrossing as listed in Table 1. As the cytoplasm donor, Taichung 65 with "Chinsurah boro" cytoplasm was used, which was made available through Dr. C. Shinjyo of University of Ryukyus. After 4-11 successive backcrosses, cytoplasm substitution lines were established in 13 kinds of genetic stocks.

To reconfirm the linkage relations and to estimate the recombination values by backcrossing, these stocks were used for crosses, and the linkage intensity obtained from backcross data was compared with that from F\2\ data (Table 2). Although all linkage relations were confirmed, there was a variation in recombination value. As suggested by Immer (1930) and Allard (1956), there was a tendency for F\2\ repulsion data to give a higher recombination value than the true value given by backcrossed progeny. The accuracy of estimation of recombination values will be improved by the use of backcrossed populations produced by the CMS genetic stocks.


Table 1. List of cytoplasmic male sterile stocks for marker genes of rice

=============================================================================
No.        Name              Marker genes    Back           Donor
                                             crosses  ===================
                                                      Cytopasm    Nucleus
=============================================================================
A- 5  MS  Akamuro         CBr,A,P,Pr,Rc,Rd,    B\7\   [ms-bo]      A- 5
                          I-Bf+  
A- 58 MS  Kokushuokuto-2  CB,A,P,Pr,Pn,Ph,wx   B\11\     "         A- 58
A-133 "   Norin-9         CBm,Ad,P             B\5\      "         A-133
A-136 "   Shiokari        CBm,Ad,P             B\11\     "         A-136
H- 21 "                   bl-1,Rc,sh           B\9\      "         H-21
H- 61 "                   d-2,CBp,A,P+,Pn,     B\7\      "         H-61
                          I-Bf+  
H- 68 "                   ri,bl-1              B\4\      "         H-68
H- 69 "                   nl-1,fs-1,CBp,A+     B\11\     "         H-69
H- 79 "                   d-2,bc-1,lg.la       B\7\      "         H-79
H-126 "                   d-6,CBp,A,P,Pl, Hg   B\11\     "         H-126
H-135 "                   d-1,gh-1,g-1         B\6\      "         H-135
H-143 "                   st-2,gh-1,Rc         B\6\      "         H-143
H-339 "                   Cl                   B\10\     "         H-339
=============================================================================


Table 2. Recombination values calculated from backcross and F\2\ data

=============================================================================
Linkage        Gene pair            Recombination    value    (%)
groups                              Backcross         F\2\
=============================================================================
            C       st-1       c    27.6+/-5.60   c    25.5+/-1.81
I           fs-1    Cl         c     0.6+/-0.30   c     0.8+/-9.21
            fs-1    Ur-1       c    27.3+/-1.89   c    27.5+/-1.39
=============================================================================
            d-2     lg         c    54.4+/-3.54   c    47.2+/-1.24
            d-2     Pr         c    43.7+/-2.54   c    52.8+/-2.16
            d-2     P          c    52.5+/-2.08   
II          Pl      lg         c    25.6+/-1.86   c    30.9+/-0.84
            Pl      spr-1      c    27.4+/-3.09   
            Pr      lg         c    26.7+/-2.72   c    28.2+/-1.31
            Pr      P          c    32.2+/-2.39   
=============================================================================
III         A       Pn         c    20.0+/-1.73   r    29.9+/-2.13
=============================================================================
IV          d-6     g-1        c     7.7+/-2.49   r    14.0+/-2.45
=============================================================================
VI+IX       gl-1    An-2       c    31.7+/-6.52   c    39.5+/-2.08
            gh-1    st-2       c    48.2+/-1.65   r    40.9+/-2.43
=============================================================================
c...Coupling phase, r...Repulsion phase



References

Allard, K.W., 1956. Formulas and tables to facilitate the calculation of recombination values in heredity. Hilgardia, 24: 235-278.

Immer, F.R., 1930. Formulae and tables for calculating linkage intensities. Genetics 15: 81-98.